1. Field of the Invention
The present invention relates to an electromagnetic control valve for an internal combustion engine and more particularly to an electromagnetic control valve for controlling the fluid flow rate by rotational movement of the valve member.
2. Description of the Background
In a typical electromagnetic control valve, a motor part for generating an electromagnetic force and a valve assembly for controlling fluid flow rate are installed in one housing. When the valve is actuating a solenoid in the motor usually generates heat (about 350.degree.-360.degree. F.), which will damage the valve members in the valve assembly. Therefore, the member for holding the coil has to be formed by heat-resisting resins or metal materials.
Furthermore a permanent magnet and a valve rotor has to be attached on the same shaft, so that coil of the motor may generate a parallel magnetic field on the permanent magnet. In order to apply such parallel magnetic field under such circumstances, the position of the coil is limited and the effective winding rate of the coil is very low.
Furthermore, the shape of the motor is complex and the cost of the motor becomes higher.
On the other hand, when the coil generates the parallel magnetic field, in the magnetic circuit a great magnetic resistance exists due to a gap between the internal and external yokes.